Breathability — what is it, and why do I need it?

Posted 25 March 2016

Whether you’re in the market for a new waterproof jacket, or you simply enjoy taking an interest in the science and technology that enhances your outdoor apparel, chances are you’ll have heard talk of ‘breathability’ fairly often. You know that breathability is a good thing. You know that you want your jacket to be breathable. But… you’re still not 100% sure you know what being ‘breathable’ actually means!

The Science of Sweating...

To understand what breathability is, and to grasp why you want your jackets, jerseys, and other apparel to be ‘breathable’, we need to take a look at the science behind gas movement, and the science of sweating.

Water vapor is a gas. And, as a gas, it’s constantly trying to mix with other gases so that it disperses more or less equally. Just about all gases do this, and it’s actually the main reason that breathability is important.

Imagine that the air inside a room is stuffy. You know that opening a window is the best way to deal with this, but why? Since gases are constantly trying to mix, opening the window gives the thick, heavier air inside a chance to meet the cooler, fresher air outside. Once this happens, the two gases can begin to mix with one another—the heavier, stuffier air leaves the room and is replaced by the cooler air from outside. The two gases have mixed, and equilibrium is achieved.

Allowing Vapor to Vacate…

If we apply this idea to clothing and sweating, the idea of ‘breathability’ begins to make sense. Your body is constantly giving off heat and moisture, even if you’re sitting completely still. Of course, exercising more or wearing thicker clothing increases the amount of heat and moisture being released. This heat and moisture, or sweat, as it’s otherwise known, rises from the surface of your skin before becoming trapped by the clothing and apparel you’re wearing.

As you know, removing thicker clothing helps to cool you down, and can help to prevent a build up of sweat. It can also help to minimise any discomfort caused by wearing sweaty clothing. Unfortunately, removing clothes also leaves you exposed to the elements, and more prone to getting cold, wet, and wind-beaten. Ideally, then, you need clothing that will allow the sweat you’re producing to escape, without allowing the elements in.

In other words, you need a garment that can breathe.

The Benefits of Breathability…

While breathability is clearly a good thing, it doesn’t increase comfort in and of itself. It doesn’t prevent sweating, or sweat build-up—to stop this, your garments will also need to wick away sweat from your skin. Breathability doesn’t actively cool you down either—while some heat will escape, heated air will still remain trapped between your skin and your apparel. Breathability, then, simply allows sweat and water vapour to pass through your garments in order to reach the cooler air outside, where it can quickly move away.

Of course, there’s plenty more going on in your technical garments which hasn’t been covered here. Next time breathability is listed as a feature, though, you’ll know precisely what it means.